1. Field of the Invention
The present invention relates to a charging device and an image forming apparatus provided with the device apparatus.
2. Description of the Related Art
In an image forming apparatus of an electrophotographic type, a charging device of a corona discharge type is used as a charging section which uniformly charges a photoreceptor which is an image bearing member to bear an electrostatic latent image thereon. Such a charging device of a corona discharge type is provided with a shield case having an opening opposing to a photoreceptor and a discharge electrode disposed in a stretched manner inside the shield case whose discharging surface is a linear, a pin array, or a needle shape. The charging device is a so-called corotron which charges a photoreceptor uniformly by applying high voltage to the discharge electrode so that a corona discharge is generated, or a so-called scorotron which provides a grid electrode between the discharge electrode and the photoreceptor so as to charge the photoreceptor uniformly by applying desired voltage to the grid electrode.
In the charging device of a corona discharge type, a discharge product such as nitrogen oxide (NOx) is produced. To be specific, by the energy released from the charging device along with the discharge of electrons, nitrogen molecule (N2) present in the air is dissociated into nitrogen atom (N), and the nitrogen atom is combined with oxygen molecule (O2) to thereby generate nitrogen oxide (nitrogen dioxide: NO2).
When nitrogen oxide is generated in this manner, the nitrogen oxide is adhered to the photoreceptor as ammonium salt (ammonium nitrate), which will be a cause of an abnormal image. In particular, in a case where an organic photoreceptor (OPC) is used as the photoreceptor, the image defection such as white voids or image deletion easily occurs by the nitrogen oxide.
To solve such a problem, Japanese Unexamined Patent Publication JP-A 2003-122187 discloses an image forming apparatus with a configuration in which a brush roller containing zeolite is caused to abut on an upward side of a photoreceptor. Furthermore, JP-A 2003-122187 discloses an image forming apparatus with a configuration in which a plate-like member containing zeolite is arranged on the upward side of the photoreceptor so as to oppose to the photoreceptor.
According to the image forming apparatus disclosed in JP-A 2003-122187, zeolite contained in the brush roller and the plate-like member has a property to adsorb the nitrogen oxide and the ammonium nitrate, and thereby it is possible to adsorb and remove the ammonium nitrate adhered on a surface of the photoreceptor with the brush roller to be frictionally sliding thereon, and adsorb and remove the discharge product such as nitrogen oxide floated in the air in a vicinity of the photoreceptor with the plate-like member. Thereby, it is possible to suppress occurrence of the image defection caused by the discharge product such as the ammonium nitrate adhered to the photoreceptor, nitrogen oxide floated in the air in the vicinity of the photoreceptor, and the like.
However, in the image forming apparatus disclosed in JP-A 2003-122187, since the brush roller containing zeolite adsorbs and removes the ammonium nitrate adhered on the photoreceptor by frictionally sliding thereon, there is a possibility that a scratch occurs on a surface of the photoreceptor and thereby the image defection due to the scratch occurs. Furthermore, in the image forming apparatus disclosed in JP-A 2003-122187, since the plate-like member containing zeolite is arranged on an upward side of the photoreceptor, it is impossible to remove the discharge product that flows toward downward side along the surface of the photoreceptor. Therefore, the image forming apparatus disclosed in JP-A 2003-122187 is not capable of sufficiently preventing occurrence of the image defection such as white voids or image deletion caused by the discharge product such as nitrogen oxide. Moreover, in the case of the charging device with a configuration in which the discharge electrode is provided in a stretched manner inside the shield case, the discharge product is retained at high concentrations in an inner space of the shield case after discharge operation, however, a configuration in which the discharge product retained in the inner space of the shield case is able to be removed without degrading charging performance is not disclosed in JP-A 2003-122187.